Normal human alveolar macrophages (HAMs) stimulated with lipopolysaccharide (LPS) selectively produce large amounts of the antiinflammatory mediator, prostaglandin E2 (PGE2). The mechanisms for this enhanced conversion of arachidonic acid by human alveolar macrophages to PGE2 vis PGH synthase and PGH-PGE isomerase are unknown. Cigarette smoking inhibits this conversion of arachidonic acid to PGE2 by alveolar macrophages. The mechanisms for this inhibition are also unknown. The goal of this research proposal is to determine the mechanism for regulation of PGE2 production by normal human alveolar macrophages and to determine how these mechanisms are altered by cigarette smoking. The overall hypothesis of these studies is that PGE2 formation is regulated in normal alveolar macrophages by regulating amounts of PGH synthase, which catalyzes the first committed step in the formation of PGE2 from arachidonic acid. A further hypothesis is that the reduced conversion of arachidonic acid to PGE2 in smokers macrophages is related to the overall oxidant stress imposed on these cells by components of cigarette smoke. The overall approach to these hypotheses will be to systematically evaluate the regulation of the conversion of arachidonic acid to PGE2 in normal macrophages and then to determine how in vivo or in vitro exposure to cigarette smoke alters each step in the conversion of arachidonic acid to PGE2. The investigators will then try to relate these defects to the overall oxidant stress placed on these cells by cigarette smoke. Future studies, separate, but directly linked to this proposal will evaluate the effects of arachidonic acid availability and 5 lipoxygenase product formation on normal and smoke exposed alveolar macrophage PGE2 formation.